It was found that the effect of jet aircrafts on the ozone layer was too insignificant to be the cause of ozone depletion. there were simply not enough aircrafts to inflict lasting harm on the ozone layer. so, in 1973, professor sherry rowland and his colleague dr. mario molina began to investigate chlorofluorocarbons, or cfcs. because they are such stable compounds, cfcs were used extensively in industry as aerosol propellants, refrigerants and in insulation foams.
so rowland and molina had two questions. first, they wanted to find out how persistent these stable cfcs are, meaning for what amount of time cfc molecules could remain in the lower atmosphere without reacting. second, the researchers also wanted to find out what might happen if these cfcs made their way into the upper atmosphere and got subjected to high-energy ultraviolet radiation there. their investigation found that, because of their stability, cfcs could remain in the air for many centuries without reacting. it was the answer to their second question that really got their interest.
they found that the breakdown of cfcs by ultraviolet radiation produces chlorine atoms:
cf2cl2(g) → cf2cl(g) + cl(g)
their next question was what would happen to the chlorine atoms that would be floating around in the atmosphere. they concluded that the chlorine could potentially react with ozone using the following reaction mechanism:
step 1 : cl(g) + o3(g) → clo(g) + o2(g) (slow step)
step 2 : clo(g) + o(g) → cl(g) + o2(g) (fast step)
predict the rate equation for the mechanism for the reaction between chlorine atoms and ozone molecules and write the overall reaction.